There are few things in this life that elicit quite the level of excitement that a two-stroke dirt bike can. The difference in the smells, sounds, tires, and overall experience is unexplainable. The RPMs do not climb steadily like they do with a four-stroke. Instead, a demon lurks at peak horsepower, in the fabled power band. Once you’ve tamed the untamable, nothing else is ever quite the same again.
If you own or intend to purchase a two-stroke, you’re probably already aware that these engines have a unique requirement. The oil that lubricates a 2 cycle engine is normally delivered via the fuel supply. This task requires a specific type of oil – not your ordinary motorcycle oil, and each manufacturer’s offerings can vary dramatically.
The best two stroke oil for your bike is the one that suits its needs best and also responds to your individual riding style. Let’s look a little closer at what makes a good two-stroke oil great.
A top-tier oil for most two-stroke applications, Motuls Two-Stroke Oil enjoys a stellar reputation. Whether racing or trail riding, you can’t go wrong when using this oil in your machine.First Checkpoint
Best 2-Stroke Oils Reviewed
These are the best two-stroke oils to keep your engine crisp and clean.
Castor-based oils like Maxima’s Castor 927 work best in demanding applications like motocross racing. Because of their tendency to produce varnish, these oils may not be suitable for low-speed riding.
Long a favorite of two-stroke motocross racers, Maxima’s Castor 927 is a go-to premix for demanding applications. It combines a proprietary modified-fatty-acid ester and a “multifunctional additive mixture” to a highly refined castor oil, reducing the buildup of varnish that can plague castor-based oils. On the plus side, castor oils like Castor 927 leave a viscous film on metal engine parts, which lubricates them for longer and in higher temperatures than any other type of 2T oil.
The downside of Castor 927 is that the film it leaves behind can gum up moving parts if not completely burned away. Coupled with the use of ethanol-containing gas, which can also leave such deposits, 2T castor oil may not be worth the trouble for casual riders. But if you’re the type that lives for the “braap” of high-revving two strokes, Castor 927 is likely a wise choice. Just be sure to insist on ethanol-free fuel – especially if your bike is vintage.
- Dependable in high-performance engines
- Reduced varnishing compared to other castor oils
- Years of proven reliability on racetracks
- Produces inoffensive sweet smell when burning
- Not suitable for oil injection systems
- Produces more varnish in low-speed machines
- Necessitates ethanol-free fuel and racing revs
A top-tier oil for most two-stroke applications, Red Line’s Two-Stroke Racing Oil enjoys a stellar reputation. Whether racing or trail riding, you can’t go wrong when using this oil in your machine.
In recent years, Red Line has gone from boutique synthetic oil manufacturer to a force in the industry. In racing circles, it is well-respected for the quality of its synthetic lubricants, and the first product it made was its Two-Stroke Racing Oil. The ester based oils have a film strength that rivals castor oil, without any tendency to smoke at slower speeds.
Up to one quarter of this oil is made up of highly refined mineral oil, though it certainly qualifies as a synthetic for the U.S. market, where the term synthetic is more of a marketing term than a quantifiable attribute. Another quarter of it is esters, with an additive package constituting the rest. Red Line claims the resulting oil resists mechanical wear better than castor oils and competing synthetics, as well as providing a 2-to-3-percent bump in horsepower. The undeniable fact is that Red Line’s 2T Racing Oil is a proven winner on tracks around the globe.
- Suitable as premix or in oil injectors
- Useful at slow speeds, can handle high speeds
- The pure synthetic base oils are attracted to metal
- Provides documented horsepower increase
- Fully synthetic is a bit misleading
- Tends to cost a bit more than some competitors
Royal Purple’s HP 2-C is a synthetic blend, but a highly refined one. It compares favorably to most other synthetic two-stroke oils, but can cost a bit less than most of them.
Royal Purple is known for its synthetic oils, and it enjoys a reputation for making high-quality motor oils. The company’s two-stroke oil, called HP 2-C, is a slightly different beast. It contains approximately one half petroleum distillates and one quarter butene, with only about one quarter of the mixture consisting of esters. However, the petroleum components are so highly refined that their long-chain properties are indistinguishable from truly synthetic oils.
So HP 2-C is actually a blended 2T oil. It boasts many of the same attributes as fully synthetic oils – good low-RPM operation and strong film strength – but it lacks one key benefit: temperature tolerance. Users sometimes complain about poor low-temperature performance in lawn equipment, though the larger ports of motorcycle engines likely keep that from being an issue in those machines.
- Often the most affordable synthetic 2T oil available
- Excellent for everyday operation in warm weather
- Strong film strength protects vital engine parts
- Usable in oil injectors and as a premix
- Less “synthetic” than some other “synthetics”
- Not suitable for sub-arctic conditions
Lucas’ Semi-Synthetic 2-Cycle Oil is an excellent blend for leisurely, low-speed riding. Its additive package keeps it stable in most fuel types and prevents the smoking that prefaces varnish and carbon deposits.
Lucas started out making oil additives, so it is a safe bet it knows a thing or two about mixing oil and petrol. The only ingredient Lucas will cop to in its Semi-Synthetic 2-Cycle Oil is naptha (10 to 30 percent). The rest of the mixture is proprietary, which is customary for synthetic oils. It contains an unnamed detergent to ease piston travel and prevent spark plug fouling.
The additives in Lucas’ 2T oil also help prevent smoking and carbon buildup, while the detergents help it stay stable in gas. It also stabilizes the fuel itself, making it an excellent choice for occasional dirt riders, especially those who can be hard on their machines. Excess smoke and carbon buildup can be a result of running your mixture to rich or too lean. Check out our guide to identify and avoid running your dirt bike too rich or too lean.
- Excellent stability for long-term storage
- Mixes well in different fuel types
- Gets along with ethanol
- Resists carbon buildup
- Contains more additives than some others
- Its ingredients are largely a mystery
Motul’s 710 two-stroke oil is an ester-based, fully synthetic product engineered specifically for modern two-cycle motorcycles. For those lucky enough to own one of these machines, it is the safe choice.
Motul’s 710 2T oil is fully synthetic and is formulated specifically for modern, late-model two strokes. It is an ester-based oil, and it exhibits profound anti-smoke properties. Its other constituent chemicals are proprietary, so there is not much to divulge about its additive package. Its viscosity makes it suitable for oil injectors or as a premix.
This is not one of the lower priced options available, but it is produced by a company with an impeccable reputation in motorcycle racing. If you are concerned about using a proper, modern 2T oil in your new two-stroke bike, it is definitely worth trying. It meets JASO and ISO standards for emissions, and of course it is API-TC certified.
- Specifically formulated for late-model two-stroke motorcycles
- Does not smoke, regardless of RPMs
- Fully synthetic and ester based
- Impervious to temperature fluctuations
- Can cost more than some of its competitors
- Ingredients are a mystery
The Venerable Two-Stroke
Internal-combustion engines such as those found on most motorcycles utilize the power of small explosions to force a piston to move through a cylinder. The piston is attached to a rod, which turns a crankshaft that eventually sends power to the rear wheel. For the system to function, a mixture of air and fuel must be drawn into the cylinder. The then piston compresses the air and fuel at the top of the cylinder, when a perfectly timed spark fires to ignite the mixture.
The force of the resulting explosion sends the piston back down the cylinder, transferring power to the crankshaft. This is called the power stroke. The gases left over after the power stroke is initiated must be expelled from the cylinder, and fresh air-fuel mixture must be drawn in and compressed again.
The majority of engines produced today are four-stroke types which have a number of distinguishing features to two stroke dirt bikes. The easiest way to tell the two apart is from a quick look at the exhaust system. 4-stroke exhausts do not have a big header pipe and sound much deeper and gruntier than a two-stroke. Here you can read more about the differences and help you decide if a 2 stroke or 4 stroke is best for you.
In these engines, each piston produces one power stroke for every four piston strokes. Each of the other three piston strokes achieves one of the necessary steps. After the power stroke, the next up-stroke expels spent gasses from the cylinder through an exhaust valve. On the next down stroke, air-fuel mixture is drawn into the cylinder, which is then compressed on the final up stroke. Check out our review of the best dirt bike pistons for more information.
Two-Strokes Are Different
The two-stroke engine achieves all of that movement of gasses in just two passes of the piston. The power stroke is used to expel spent gasses, while the up stroke draws in a fresh charge of air-fuel mixture. It usually does this by creating a vacuum in the crankcase. The fresh charge draws into the cylinder on the upstroke, with the piston covering the intake and exhaust ports when they are not needed. The term for utilizing the crankcase in this way is scavenging.
Four-stroke engines use the crankcase as a sump. Oil collects in the bottom of the sump, bathing the moving engine parts in lubricant. Because of the constant flow of gasses in a crankcase-scavenged two-stroke, using the crankcase as an oil sump is not practical. Oil must therefore be either mixed with the fuel or injected into the engine bearings with a pump. Otherwise, metal-to-metal contact will occur, causing friction and heat that would inevitably lead to engine failure. You should consider riding with engine coolant or antifreeze to help with overheating – read our reviews of the best motorcycle coolant here.
The engineers give a thorough explanation of the function of a modern two-stroke engine, as does Kevin Cameron in this article in Cycle World.
Selecting The Right Two-Stroke Oil
In the earliest days of two-stroke engines, the only oil available was petroleum-based. Essentially no better than common motor oil, petroleum-based two-cycle oil mixed poorly and burned incompletely, producing a putrid smell and clouds of black smoke from the exhaust. There is very little of this type of two-stroke oil still available today. What follows are the other three main options on the market and see which is the best two stroke oil for your bike.
Castor-based oils are exactly what they sound like: oil made from castor beans. The beans are pressed and their oils are extracted and processed to produce a highly refined vegetable oil. In the past glory days of two-stroke motocross – before the four-stroke engine took over the sport – castor oil was the main choice on the circuit. The reason for its dominance is the same reason castor-based oils are still popular among the few holdovers racing two-strokes (source).
Castor oil sticks to metal parts, lubricating them better than even modern synthetics can. It readily clings to hot spots, lubing the parts that need it most. However, that film strength also causes varnish deposits that must be removed, though racing crews tear down their engines so often that it’s a moot point.
Synthetics may mix better with fuel, but nothing yet available lubricates better. The noticeably sweet smell of burning castor oil is just a bonus. This article describes the benefits of castor oil, its production and its promise as a renewable resource. We went on the search for the best smelling 2 stroke oil and narrowed it down to a few options – just about all of them are castor based.
All motor oil is made of long-chain polymers. Conventional motor oil comes that way out of the ground, though it is highly refined to retain only the properties that chemical engineers desire. Synthetic oil starts out as much shorter chains, which are then combined to form long chains of polymers. As oil ages and undergoes the stresses of engine operation, those long chains break down, causing the polymer chains to get shorter. The advantage of synthetic oil is that it tends to resist that breakdown for longer, and under hotter conditions.
That doesn’t mean that synthetic motor oil is necessarily better than conventional. This Kevin Cameron article in Cycle World magazine explains why that is so. However, remember that petroleum-based two-stroke oil tends to smoke more than other types. That is especially true at slower speeds and cooler engine temperatures, where the majority of motorcycles spend their lives. Synthetic oils typically include additive packages that help them resist smoking and still retain their lubrication properties under a broad array of conditions.
A 2T oil labeled as a synthetic blend will normally be a mixture of a synthetic base oil and either a petroleum mineral oil or castor oil. Ideally, these oils will provide all the benefits of their constituent parts – petroleum (low cost), castor (lubrication) or synthetic (versatility). However, many of these blends cut costs to produce a cheap product, often one intended for lawn equipment. Like when buying a helmet or boots, it is best to stick with trusted brands and with those intended for motorcycles.
A Word On Injector Pumps
In the 1980s, manufacturers began to offer two-strokes with an oiler to inject lubricant into the engine, eliminating the need to premix oil and fuel. Some two-stroke oils are too viscous to pass through the ports of oil injectors, and riders with these types of systems should avoid those products. If you have an oil injector on your bike, look for confirmation that the oil you are purchasing clearly states it is for Autolube or oil-injector applications.
The American Petroleum Institute (API) certifies two-cycle oils with its API-TC label. This standard is a bare minimum. The Japanese Automotive Standards Organization’s JASO-M345 standard and that of the International Organization of Standardization (ISO) better reflect modern emissions requirements. Look for those standards on the label of any two-stroke oil to ensure it meets the highest specifications.
Were this a question of the best two stroke oil for certain applications, or perhaps for saving money, it would have been a tighter competition. But the issue at hand is which is the best two stroke oil… period. While that question is certainly subjective to some extent, for my money the winner has to be Red Line Two-Stroke Racing Oil.
It offers the most versatility in usage – from chainsaws to motocross – and leaves little evidence behind after it’s been burned. For racers all the way down to beginning trail riders, there is no better option.